Electron Spin Resonance Spectroscopy for the Identification of Irradiated Foods with Complex ESR Signals

Abstract

Electron spin resonance (ESR) spectroscopy for the detection of irradiated food could provide complex spectra due to the presence of different nonirradiation-specific paramagnetic species in the sample. Particularly, ESR signals from naturally present Mn2+ could limit the ESR-based detection of irradiated foods of plant origin. In this study, the effects of different concentrations of Mn2+ on the radiation-specific ESR spectral features of radiation-induced crystalline sugar or cellulose radicals were examined. Soy sauce powder with Mn2+ was irradiated at 10 kGy and its effect on the identification of radiation-induced sugar (pak choi, 10 kGy) and cellulose (red pepper powder, 10 kGy) radicals was evaluated. In the blends of red pepper and soy sauce, the left (g 1 = 2.025) and central (g 2 = 2.005) peaks of the cellulose signal significantly decreased with the decline of red pepper content (R 2 = 0.9384, g 1; 0.8819, g 2). However, the right peak (g 3 = 1.988) significantly increased (R 2 = 0.9353, g 3) with an escalation in the soy sauce content. The cellulose radical signals were identifiable from the blends containing more than 50 % red pepper powder. In the blends of soy sauce and pak choi, the ESR intensity of crystalline sugar radicals significantly decreased with the decline in pak choi content (R 2 = 0.9887). However, Mn2+ signal didn’t overlap with the sugar radical signals. The ESR signals from radiation-induced crystalline sugar remained unaffected; however, the signals from cellulose radicals provided a reduced detectionability depending upon the concentration of Mn2+ in the sample.